Optical amplifiers utilize a gain medium to amplify optical radiation. In an amplifier, a source excites the gain medium to produce a population inversion between high and low energy states of the gain medium. The excited gain medium can amplify optical radiation at energies overlapping the energy differences between the high and low energy states of the population inversion because stimulated emission of radiation from the medium is more efficient than absorption of light. In general, a laser utilizes a cavity to supply feedback to an excited gain medium to cause amplified spontaneous emission. A laser cavity can include a series of optical components, such as mirrors, arranged relative to the gain medium to reflect radiation back into the cavity and thereby provide feedback.